To take out anti-theft signals by means of a rational mechanism and enhance the convenience of operations.

In a signal takeout mechanism for a lock, a horizontal shaft 28 is provided with a control gear 9 for meshing with cylinder engagement teeth 25, and is provided also with an output member 10 having an engagement projection 31 which engages the control finger section 30 of the control gear 9. An alarm switch 11 capable of abutting the switch drive 35 of the output member 10 is disposed within a lock box 1, and when a cylinder tumbler 7 is rotated by a predetermined amount by means of a master key, a deadbolt 3 projects from a front 2. When the master key is further rotated by +α, the cylinder tumbler 7 rotates against the spring force of an energizing spring 12 mounted within the lock box 1 and the control gear 9 rotates in combination with the cylinder tumbler 7, with the output member 10 moving the alarm switch 11 to an on position under control of the control gear 9.